1. Field of the Invention
This invention relates to a combination seismic response and wind control system for restraining the vibration of a structure against vibrational disturbances caused by earthquake and wind forces impacting on a structure.
2. Description of the Prior Art
Conventional seismic response and wind control systems installed on structures are of active and passive types. Active seismic response and wind control systems are disclosed in Japanese Patent Laid-open Nos. Sho 62-268478 and Sho 63-156171. These systems include weights and vibrators positioned on the tops of structures. The vibrators vibrate the weights in a controlled manner responsive to the vibrational forces on structures caused by earthquake and wind, whereby the vibration of the structure is attenuated.
As a passive seismic response and wind control system, Japanese Patent Laid-open No. Sho 63-114773 has disclosed a dynamic vibration absorber, in which a weight having a mass corresponding to about one hundredth of the weight of the structure is connected to the structure through a spring having a predetermined natural period of vibration, whereby the vibration of the structure is damped. Also, Japanese Patent Laid-open No. Sho 63-254247 has disclosed a pendulum type dynamic vibration absorber in which a suspension member is used as connecting means for giving a specified natural period to the dynamic vibration absorber.
An active seismic response and wind control system can be expected to exceed the capacity of a passive seismic response and wind control system. However, the active seismic response and wind control system requires external energy to operate the vibrator, whereas the passive seismic response and wind control system does not depend on an external source of energy. Thus, while the active seismic response and wind control system is preferable to a passive seismic response and wind control system, no seismic response and wind control is obtained if the supply of external energy is lost in an emergency.